Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. Emulsion aggregation toners may be used in forming electrophotographic images. Emulsion aggregation techniques may involve the formation of a polymer emulsion by heating a monomer and undertaking batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Emulsion aggregation/coalescing processes for the preparation of toners are illustrated in a number of patents, such as U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,344,738, 6,593,049, 6,743,559, 6,756,176, 6,830,860, 7,029,817, and 7,329,476, and U.S. Patent Application Publication Nos. 2006/0216626, 2008/0107989, 2008/0107990, 2008/0236446, and 2009/0047593. The disclosures of each of the foregoing patents are hereby incorporated by reference in their entirety.
Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Patent Application Publication No. 2008/0153027, the disclosure of which is hereby incorporated by reference in its entirety.
The incorporation of these polyesters into the toner requires that they first be formulated into emulsions prepared by solvent containing batch processes, for example solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE), which are both time and energy-consuming. In both cases, large amounts of organic solvents, such as ethyl acetate, ketones or alcohols, have been used to dissolve the resins, which may require subsequent energy intensive distillation to form the latexes, and are not environmentally friendly.
Solventless latex emulsions have been formed in either a batch or extrusion process through the addition of a neutralizing solution, a surfactant solution and water to a thermally softened resin as illustrated, for example, in U.S. Patent Application Publications Serial Nos. 2009/0246680 and 2009/0208864, the disclosures of each of which are hereby incorporated by reference in their entirety.
Improved processes for the preparation of polymer latexes suitable for use in a toner remain desirable.